In a typical ultrasound guided procedure, a doctor will place a small, handheld probe known as a transducer on a patient's skin. The transducer converts electrical energy to acoustic energy. Acoustical energy is transmitted from the transducer and into the patient's body in the form of sound waves. The transmitted sound waves are either reflected back towards the transducer or absorbed by the medium, depending on the acoustical impedance. The reflected sound waves are converted into electrical signals which are used to form a real time two-dimensional image of a portion of the patient's body. This ultrasound image may be used to assist a health professional with locating a point where an invasive medical device, e.g., a needle, is inserted. After locating the correct insertion point, the health professional may then begin the medical procedure, such as insertion of a catheter, administration of a local anesthetic, or removal of tissue as in a biopsy.
Before beginning a procedure, it is necessary to cover the ultrasound device to assure that sterility is maintained during the procedure. Typically, a sterile sleeve or condom made of a flexible, sterilizable material is draped over the device to form a sterility barrier. A sterility barrier is intended to refer to a seal, bond, covering, etc. that is effective in preventing micro-organisms or other contaminates from migrating from within the sleeve, condom, etc. to the exterior, sterile environment. An acoustic coupling gel is placed in the sleeve before placing the transducer in the sleeve to ensure consistent contact between the sound transmitting/receiving end or head of the transducer and the sleeve. This contact is necessary to ensure there are no artifacts in the ultrasound image due to the presence of air pockets between the head and sleeve. The coupling gel may be applied to the sleeve at the time of the procedure or the gel may be pre-applied to the sleeve. In the later case, a breakable seal is usually included in the sleeve to protect the gel from contaminates. This type of cover is described in U.S. Pat. No. 5,676,159. The end opposite the head of the transducer is typically sealed using a rubber band wrapped around the sleeve.
Brackets are sometimes provided with an ultrasound device for purposes of mounting a needle guide. The needle guide is used to facilitate a longitudinal or transverse type ultrasound guided needle insertion procedure. In the “transverse” type, the guide is arranged so that the needle is inserted into the patient along a plane transverse to the ultrasound image plane. In the “longitudinal” type, the needle is inserted into the patient in a plane parallel to the ultrasound image plane.
One known ultrasound device for assisting a health professional with needle placement in a body is the ilook™ personal imaging tool, sold by SonoSite®, Inc., which includes a series of removable needle guides and a bracket for mounting the needle guides to the transducer. The device is used to place a needle at a target beneath the skinline by real-time visual identification of the target via an ultrasonic image. The needle guide is arranged on the transducer so that a needle received therein will extend approximately perpendicular to the sonic scanning plane. Thus, the SonoSite®, Inc. device is a transverse-type device. A sterile needle guide is snap-fit on the bracket. There is more than one-type of needle guide to choose from. The choice depends upon the distance between the skinline and the needle's target in the body. The needle guide has a door that can be locked in a closed position by a slidable switch, thereby retaining the needle shaft between the door and a semi-circular recessed area. The needle is placed in this recessed area and the door is closed to hold the needle therein. The transducer with needle is then placed on the skinline and the top of the vessel is located via the sonic image. The needle is then inserted into the body. After the needle has reached the target, the transducer is removed from the needle, which requires a manual unlatching of the door of the needle guide. A related needle guide is described in U.S. Publication No. 2005/0131291.